the eeps Data Zoo
curator:Tim Erickson
 zoo home eeps home products projects
 Amortization

Here we have data from an Internet mortgage calculator. Imagine borrowing \$100,000 for fifteen years at 5%.

(We used this calculator, but there are a lot out there. We needed to do a small amount of text processing to get rid of the commas and dollar signs.)

month is the time variable; what month are we in?
interest is how much you pay in interest that month.
principal is how much you pay to the principal that month.

What function models principal well?

What do that function's parameters mean?

Can you tell whether the bank is rounding?

monthinterestprincipalbalance
1416.67374.1399625.87
2415.11375.6999250.19
3413.54377.2598872.94
4411.97378.8298494.11
5410.39380.4098113.71
6408.81381.9997731.72
7407.22383.5897348.15
8405.62385.1896962.97
9404.01386.7896576.19
10402.40388.3996187.80
11400.78390.0195797.79
12399.16391.6495406.15
13397.53393.2795012.88
14395.89394.9194617.97
15394.24396.5594221.42
16392.59398.2093823.22
17390.93399.8693423.35
18389.26401.5393021.82
19387.59403.2092618.62
20385.91404.8892213.74
21384.22406.5791807.17
22382.53408.2691398.91
23380.83409.9690988.94
24379.12411.6790577.27
25377.41413.3990163.88
26375.68415.1189748.77
27373.95416.8489331.93
28372.22418.5888913.35
29370.47420.3288493.03
30368.72422.0788070.96
31366.96423.8387647.13
32365.20425.6087221.53
33363.42427.3786794.16
34361.64429.1586365.01
35359.85430.9485934.07
36358.06432.7485501.33
37356.26434.5485066.79
38354.44436.3584630.45
39352.63438.1784192.28
40350.80439.9983752.29
41348.97441.8383310.46
42347.13443.6782866.79
43345.28445.5282421.28
44343.42447.3781973.91
45341.56449.2481524.67
46339.69451.1181073.56
47337.81452.9980620.58
48335.92454.8780165.70
49334.02456.7779708.93
50332.12458.6779250.26
51330.21460.5878789.68
52328.29462.5078327.17
53326.36464.4377862.74
54324.43466.3777396.38
55322.48468.3176928.07
56320.53470.2676457.81
57318.57472.2275985.59
58316.61474.1975511.40
59314.63476.1675035.24
60312.65478.1574557.09
61310.65480.1474076.95
62308.65482.1473594.81
63306.65484.1573110.66
64304.63486.1772624.50
65302.60488.1972136.31
66300.57490.2371646.08
67298.53492.2771153.81
68296.47494.3270659.49
69294.41496.3870163.11
70292.35498.4569664.67
71290.27500.5269164.14
72288.18502.6168661.53
73286.09504.7068156.83
74283.99506.8167650.02
75281.88508.9267141.10
76279.75511.0466630.06
77277.63513.1766116.90
78275.49515.3165601.59
79273.34517.4565084.14
80271.18519.6164564.53
81269.02521.7764042.75
82266.84523.9563518.80
83264.66526.1362992.67
84262.47528.3262464.35
85260.27530.5361933.82
86258.06532.7461401.08
87255.84534.9660866.13
88253.61537.1860328.94
89251.37539.4259789.52
90249.12541.6759247.85
91246.87543.9358703.92
92244.60546.1958157.73
93242.32548.4757609.26
94240.04550.7657058.50
95237.74553.0556505.45
96235.44555.3555950.10
97233.13557.6755392.43
98230.80559.9954832.44
99228.47562.3354270.11
100226.13564.6753705.45
101223.77567.0253138.43
102221.41569.3852569.04
103219.04571.7651997.29
104216.66574.1451423.15
105214.26576.5350846.62
106211.86578.9350267.68
107209.45581.3449686.34
108207.03583.7749102.57
109204.59586.2048516.37
110202.15588.6447927.73
111199.70591.0947336.64
112197.24593.5646743.08
113194.76596.0346147.05
114192.28598.5145548.53
115189.79601.0144947.53
116187.28603.5144344.01
117184.77606.0343737.99
118182.24608.5543129.43
119179.71611.0942518.35
120177.16613.6341904.71
121174.60616.1941288.52
122172.04618.7640669.76
123169.46621.3440048.43
124166.87623.9339424.50
125164.27626.5238797.98
126161.66629.1438168.84
127159.04631.7637537.09
128156.40634.3936902.70
129153.76637.0336265.66
130151.11639.6935625.98
131148.44642.3534983.63
132145.77645.0334338.60
133143.08647.7233690.88
134140.38650.4133040.47
135137.67653.1332387.34
136134.95655.8531731.49
137132.21658.5831072.92
138129.47661.3230411.59
139126.71664.0829747.51
140123.95666.8529080.67
141121.17669.6228411.04
142118.38672.4127738.63
143115.58675.2227063.41
144112.76678.0326385.38
145109.94680.8525704.53
146107.10683.6925020.84
147104.25686.5424334.30
148101.39689.4023644.90
14998.52692.2722952.62
15095.64695.1622257.47
15192.74698.0521559.41
15289.83700.9620858.45
15386.91703.8820154.57
15483.98706.8219447.75
15581.03709.7618737.99
15678.07712.7218025.27
15775.11715.6917309.58
15872.12718.6716590.91
15969.13721.6615869.25
16066.12724.6715144.57
16163.10727.6914416.88
16260.07730.7213686.16
16357.03733.7712952.39
16453.97736.8312215.57
16550.90739.9011475.67
16647.82742.9810732.69
16744.72746.079986.62
16841.61749.189237.44
16938.49752.308485.13
17035.35755.447729.69
17132.21758.596971.11
17229.05761.756209.36
17325.87764.925444.44
17422.69768.114676.33
17519.48771.313905.02
17616.27774.523130.50
17713.04777.752352.75
1789.80780.991571.76
1796.55784.24787.51
1800.00787.510.00

<text form of the data>

 ©2003 eeps media 866.341.3377 or Last updated February 14, 2007 supported by NSF award DMI-0216656